To ensure that a mobile device (e.g., a wireless telephone) receives a desired signal, most wireless networks incorporate one or more techniques for assigning the mobile device to an appropriate base station. A typical wireless network may contain tens or hundreds of base stations set up throughout a geographic region to service thousands of mobile devices. Generally speaking, the base stations remain fixed while the mobile devices are designed to move from place to place. As a mobile device moves from one region to another, the signal it is receiving or transmitting may be handled by a different base station. That is, a particular mobile device may be “handed off” from one base station to another as it moves from one region to another.
There exist techniques for determining which base station is the appropriate or most desired base station to service a particular mobile device. For example, one technique involves measuring the signal strength of a pilot tone transmitted by a mobile device. In this technique, the pilot tone transmitted by a single mobile device is received by multiple base stations. At each base station (or alternatively, at the mobile device if the pilot tone is transmitted by the base station), the signal strength is measured. The base stations are then ranked based on the relative signal strength measured. The base station having the highest signal strength is given the highest ranking while the base station having the weakest signal strength is given the lowest ranking.
However, techniques that assign mobile devices to base stations based solely on signal strength have their drawbacks. One drawback is that such techniques fail to take into account “interference” from other mobile devices that are assigned to the same base station. That is, the signal from a mobile device, as measured at a given base station, may be subject to interference from other mobile devices using the same base station. This interference factor is not considered by existing assignment techniques.
In addition, techniques that assign base stations based simply on signal strength are not flexible enough to assign the most efficient transmit power level to a given mobile device under a set of given channel conditions.
Accordingly, it is a desire of the present invention to provide for techniques which assign mobile devices to base stations which take into account interference from other devices which may be assigned to the same base station and which select an appropriate transmit power level for data communications given a set of channel conditions.